Train stop and cab signal system



A. E. HUDD May 23, 1933.

TRAIN STOP AND CAB SIGNAL SYSTEM Original Filed Aug. 1, 1928 3 Sheets-Sheet 7'0 BRAKE APPL/CA 70/? VALVE May 23, 1933. A. E. HUDD TRAIN STOP AND CAB SIGNAL SYSTEM Original Filed Aug. 1, 1928 3 Sheets-Sheet 2 ISHSHSHSHSHSHS'S IIIIHHI'IIIIIIIIII '1 n A/[illlllillllilllIHIHWIIII 1 n\\\ I n llll llH ll ll'fl illik May 23, 1933. A. El. HUDD TRAIN STOP AND CAB SIGNAL SYSTEM Original Filed Aug. 1, 1928 3 Sheets-Sheet 3 Patented May 23, 1933 [UNITED STATES PATENT OFFICE ALFRED E. HUDD, OF CHESHAM BOIS, ENGLAND, ASSIGNOR, BY MESNE ASSIGNMENTS,

TO ASSOCIATED ELECTRIC LABORATORIES, INC., OF, CHICAGO, ILLINOIS, A CORPO- RATION OF DELAWARE TRAIN STOP AND GAB SIGNAL SYSTEM Original application filed August 1, 1928, Serial No. 296,652, now Iatent No. 1,779,612, dated September 27, 1932. Divided and this appl cation. filed March 6, 1930, Serial No. 433,549. Renewed November The present invention relates in general to train stop systems, but is particularly concerned with the provision of a train stop system of the intermittent inductive type and wherein cab signals are provided for indicating the traffic conditions ahead, and is a division of the co-pending Hudd application, Serial No. 296,652, filed August 1, 1928, which on September 27, 1932, issued as Patent No. 1,779,612.

Some of the main features of the present invention are: to provide a system of circuits and mechanism on a locomotive for giving three distinct signalling indications in the cab, for indicating as many different trafiic conditions ahead and for giving these indications independently of, or in conjunction with, a train stop system; to provide a system of the foregoing character which requires but one receiver relay or impulse receiving unit on-the locomotive and only two trackway elements for each block of the trackway; to provide a trackway electromagnet capable of producing alternatively, either of two magnetic fields at right angles to each other; and in fact, to provide an extremely simple train stop system as hereinafter claimed.

In the accompanying drawings, Fig. 1 diagrammatically disclose the locomotive equipment of the train stop system; Figs. 2, 3, and 41- diagrammatically show permanent and electromagnetic trackway elements, respectively, with the diagrammatic sketches of the receiver relay, shown in the lower portion of Fig. 1, superimposed thereon to illustrate the influence the trackway elements have upon the receiver under various trafiic conditions; while Figs. 5 and 5A illustrate sections of trackway with associated circuits and apparatus for controlling the locomotive equipment of Fig. 1.

The valve structure diagrammatically disclosed in the upper part of Fig. 1 is a somewhat simplified modification of that shown in the co-pending Kelly application, Serial No. 292,996, filed July 16, 1928. This valve, like the one in the former application, is designed for insertion in the brake line in substitution for the double heading cook, a double heading cock being part of the present valve structure. The purpose of this valve is to initiate an automatic service application of the brakes; to prevent the release of an automatic brake application until a predetermined time interval has elapsed, and to permit an emergency application of the brakes at any time.

This valve has a main body 6, having an opening 7 for connection with the usually provided brake applicator and an opening 8 for connection with the brake pipe line. Inside the valve body, a number of ports 101 l-, inclusive, are provided all of which extend from a milled surface, forming a slide valve seat, 15. The port 10 connects with the opening 8 and has a branch 10 connecting with a second portion of the valve body which will subsequently be described. The port 11 extends downward a short distance from the seat and then connects with atmosphere. The port 12 extends directly downward and connects with atmosphere. The port 13 extends downward parallel to the port 12, but is connected with a timing reservoir 50. The port 14 extends downward a short distance and then extends horizontally into connection with a port 49. The right portion of the valve body has a slide valve seat 36 provided with a large exhaust port 37 and in which seat the other end of the previously mentioned port 10 terminates.

The left portion of the valve structure is in the form of a cylinder, in which is mounted an automatic brake applying piston 19, having connected to the right thereof, a slide valve member 20, which lies against the valve seat 15 of the valve body. Connected with the left part of the piston 19 is a cup-like member containing a compression spring 21.

The cup-like member on the piston 19 telescopes into a second cup-like member 70 forming an air chamber 71 within these cu like members and a secondary air chamber 42 surrounding these cup-like members. Two orifices, 22 and 23, connect these chambers, while an orifice 24 connects the chamber 71 with the opening 7. Immediately below and forming a part of chamber 72 is an extended portion of the valve body having a port 49 connecting with an exhaust whistle 5. The port 49 is adapted to benormallymaintained closed by an associated electro pneumatic valve EPV when energized. A cut-out element 28 is, however, provided which may be turned up to mechanically close the port 49. This cut-out in practice is ordinarily provided with a seal, which must be broken before the same can be turned up to cut out the control by the electro pneumatic valve EPV.

Referring now tothe right portion of the valve member, a dividing member 9 serves as a bearing for a shaft 31, carrying the valve member 20 and as a stop for an emergency piston return spring 33. Immediately to the right of the spring 33 is an emergency brake applicator piston 32. This piston operates the slide valve member 34 over a slide 7 valve seat 36, and at right angles thereto is a double heading cock having a handle 43.

\ through the usual brake applicator valve (not shown) into opening 7 of the brake valve structure, through the passage 7' of the slide valve member. through port 10 and the opening of the double heading cock and thence into the opening 8 and into the brake pipe line. Owing to the orifice 24 in piston 19 and because of the orifices 22 and 23. brake pipe pressure is also built up in chambers 71 and 72. Also because of the orifices in element 9 and piston 32, brake pipe pressure is built up on both sides of the piston 32. The springs 21 and 33 are therefore normally effective to hold the pistons 19 and 32 to the right in the position in which they are shown. If the electro pneumatic valve EPV is decnergized, air exhausts through the outlet port 49 and through the whistle 5 at a greater rate than brake pipe air is permitted to enter chamber 72 through the restricted orifices 24, 23, and 22. Consequently, after the pressure in chamber 72 falls to a point where the ressure upon the right-hand side of the service application piston 19 is sufficient to overcome the spring 21.-in chamber 72 (approximately six seconds. 'as designed) the service brake application piston 19 will begin to move and will first close orifice 23. When the orifice 23 closes, the air supply to chamber 72 is greatly reduced and the piston 19 with the slide valve member 20 will quickly move to the extreme left.

The piston carries with it the slide valve 20, which, in its operated position, closes the air path formerly existing between openings 7 and 8 and connects the latter opening to atmosphere by way of the port 10, passage 90, and exhaust port 11, to produce an automatic brake application. The slide valve member also disconnects the timing reservoir from connection with atmosphere by way of ports 13 and 12 and instead connects this reservoir with port 14 for a purpose which will subsequently be made clear. 7

To restore the piston 19 and slide valve member 20 to their initial position, the electro pneumatic valve EPV must be again energized to close the port 49. This permits the pressure on the left of the piston 19 190 again build up to approximately that on the right of this piston. The capacity of chambers 71 and 72 is very limited and in order to prevent practically immediate automatic release of the brakes following the energization of the valve EPV the timing reservoir 50 was brought into communication with the chambers 72 and 71. Because of the restricted orifice 22 and the capacity of reservoir 50 an appreciable time elapses after re: energization of the electro pneumatic valve before the piston 19 and its valve member are returned.

The receiver relay shown in the lower half of Fig. 1 is of the same general character as that shown in the co-pending Hudd ap plication, Serial No. 281.656, filed May 31, 1928. The present relay, however, has somewhat different magnetic circuits and has three armatures instead of two. The rela is built into a non-magnetic casing 51, which is suspended from a vehicle in inductive relation with the track magnets shown in Figs. 2 to 5A, inclusive, and which will be do scribed later. The relay consists of three inductor planes 52, 53, and 54, having pole pieces 77-83, for attracting three armatures 55, 56, and 57. The free ends of armature are of north polarity, being polarized so by a small permanent magnet 58; the free ends of armature 56 are of south polarity, being so polarized by the action ofthe permanent magnet 58 and a second permanent magnet 59, while the free ends of armature 57 are of north polarity due to the mid-portion of the armature being associated with the north pole of the permanent ma et 59. The inductor planes 52, 53, and 54 are made of soft iron and therefore are normally inert, but since the armatures are polarized by the permanent magnets 58 and 59 these armatures will remain magnetically biased to either associated inductor plane pole piece to which they have been moved. Associated with the pole piece 80 is a winding 60 which is adapted to be energized when a key 61, in the cab of the vehicle, is actuated and when energized is effective to overcome the opposing bias produced by magnets 58 and 59 and moves the armature 56 lnto engagement with the pole piece 80.

Referring now to Figs.2, 3, and 4, the trackway magnets and their influence on the receiver relay of Fig. 1 will next be described. A permanent magnet trackway unit 95 simply consists of a number of permanent bar magnets arranged to function as one large permanent magnet, with the polarity as indicated on the drawings. This magnet is very powerful compared to those in the receiver and consequently, if the receiver R of Fig. 1 is passed over the permanent magnet unit the biasing efl'ect produced by magnets 58 and 59 will be overcome and armatures 55, 56, and 57 will be rotated in a clockwise direction into the position in which they are shown in Fig. 2, for the reason that when the receiver unit passes within inductive relation of the field produced by the trackway magnet 95, the pole piece of the inductor plane 52 becomes of strong north polarity, while the pole piece of the inductor plane 53 becomes of south polarity. Since the armatures 55 and 57 are polarized north, due to the presence of magnets 58 and 59, a repelling action will occur between these armatures and their associated pole pieces '77 and 81 while an attractive force will be set up for these armatures by pole pieces 78 and 82. The armature 56 is also rotated into association with the pole piece 79 because this armature is of south polarity. The pole piece 80 assists the pole piece 79 by the repelling action it has on the armature 56.

The electromagnet trackway elements shown in Figs. 3 and 4 are alike and consist of rectangular units having the same general outline as the permanent magnet 95. These units have four windings 9699, inclusive. When the windings 98 and 99 are energized, a magnetic field of the same strength as that of the permanent magnet is set up in the opposite direction to that set up by the permanent magnet 95, as indicated in Fig. 3. It will be obvious, therefore, that when the receiver R- passes over this trackway element, with the windings 98 and 99 energized, armatures 55, 56, and 57 will be rotated in a counter-clockwise direction into the position in which they are shown in Fig. 1 and as diagrammatically shown in Fig. 3.

If, alternatively, windings 96 and 97 are energized when the receiver R passes over the electromagnet trackway element, as illustrated in Fig. 4, a magnetic field similar to, but at right angles to that set up by windings 98 and 99 is set up and consequently, the pole piece of the inductor plane 54 becomes of south polarity, while the pole pieces of the inductor planes 52 and 53 become of north polarity. Since the polarity induced in the inductor planes 52 and 53 is the same, the elfect produced by them is substantially neutral and therefore the associated armatures 55 and 56 remain in the position to which they were moved by passing over a permanent magnet trackway element. The armature 57, however, is rotated in a counterclockwise direction due to the attractive influence set up in the pole piece 83 or" the inductor plane 54. It should be noted that as the receiver relay R passes out of the inductive field of the elect-romagnet trackway elements, the inductor planes 52 and 53 will pass through the field of the S poles of the trackway magnets which may induce weak magnetism of south polarity in the pole pieces of these inductor planes, but without effect since when they are of like polarity they will not tend to operate their armatures.

Referring now to Figs. 5 and 5A, the track circuits and arrangements of the trackway magnets will be described. In Fig. 5 a portion of block A, ablock B, and a portion of a block C are shown; while in Fig. 5A a continuation of the block C, a block D, and a portion of a block E are shown. These blocks are divided by track insulation 100. The presence of vehicles in block A and block D is indicated. At the exit of each block, it will be noted, a permanent magnet trackway element is placed alongside the track. In advance of each of these permanent magnet trackway elements is placed an electromagnetic trackway element. Each of these magnets is so spaced that slightly more than sis: seconds will be consumed by a train traveling at any speed above a very lo speed in traversing the distance between them. At the entrance of each block, a three position polarized relay is connected across the trackway rails for controlling the current supply to the trackway element, located at the exit end of the adjacent block and to also supply current to a similar polarized trackway relay at the entrance end of the adjacent block. In the track circuits illustrated it is assumed that the block E and the next block in advance thereof are both unoccupied. Under these circumstances, as will readily appear hereinafter, the current supplied to the rails of block E and the polarized track relay 105 will be in such a direction as to cause the armatures 106 and 107 of this relay to be rotated into engagement with their leftcontacts. With the armatures 106 and 107 in this position an operating circuit for the polarized relay 104, at the entrance cnd oit the block D, may be traced from the negative terminal of battery 121, through the left contact and armature 106 of the relay 105, the armature 1.07 and its left contact. through the windings 98 and 99 ot the electromagnetic trackway elements. the rail 108. the w nding of the polarized relay 104, to rail 109. conductor 110, and to the positive terminal of the battery 121. The current flow to the relay 104.- is in" the appropriate direction to cause it to move its armatures 126 and 127 into engagement with their left contacts, so that current supplied over the block C to the polarized relay 103 will be in the appropriate direction to cause it to move its armatures 136 and 137 into engagement with their left contacts. However, in the present illustration, owing to the presence of a vehicle 181 in block D, the polarized relay 104 receives no current and consequently its armatures 126.and 127 drop to their neutral or mid position. With the armatures 126 and 127 in this position, a circuit for the polarized relay 103 is completed which extends from the positive terminal of the trackway battery 140, through the mid contact and armature 126, armature 127 and its mid contact, the conductor 112, the resistance 111, the lower rail of block C, through the winding of relay 103, the upper rail of block C, and the conductor 150 to the negative terminal of the battery 140. The current flow to the polarized relay 103, it will be noted, is in the opposite direction to that supplied to the relay 104 and therefore the polarized relay 103 rotates its armatures 136 and 137 into engagement with their right contacts. With the armatures 136 and 137 in this position, current for operating the polarized relay 102 at the entrance of block D is supplied from the negative terminal of battery 131, through the right contact and armature 136 of the polarized relay 103, at: mature 137 and itsright contact, through the windings 97 and 96 of the associated trackway electromagnet, the lower rail of block B, theiwinding of the polarized relay 102, the upper rail of block B, and the conductor 160 to the positive terminal of battery 131. The current flow to the polarized relay 102 is therefore in the same direction as that supplied to relays 104 and 105 and consequently the armatures 146 and 147 of the relay 102 will be rotated into engagement with their left contacts, thereby completing the circuits for feeding battery current to the track relay of the block A in the same direction as it is being fed to the track relay 102.

We will now consider the circuits and apparatus under control of the armatures 55, 56, and 57 of the receiver. These armatures as shown in Fig. 1 are in the positions they assume while the vehicle is passing through a block which was entered under clear trafiic conditions. Under these circumstances, a circuit for the green lamp 62 extends from the negative terminal of the battery 84, over conductor 71', the armature 57 and its contact member 57 contact 75, through the conductor 88, the armature 55 and its contact member 55, the contact 73, conductor 65, the lamp 62, conductor 69, conductor 67, contact 74, contact member 56' and the associated armature 56, conductor 86 and through the contact and acknowledging key '61 to the positive terminal of the battery 84. The green block A, Fig. 5, and that the vehicleis travelsing in the direction indicated by the arrow, As the receiver R passes" over and within the influence of the permanent magnet trackwayelement its armatunes 55, 56, and 57 are rotated into the position in which they are shown in Fig. 2. Armature 55, at its contact 155 member 55', breaks a point in the traced circuit through contact 73 for the green lamp 62 thereby extinguishing the green lamp and at its contact 72 prepares a point in a circuit for the yellow lamp 63; at its armature 56 the traced circuit through contact member 56' and contact 73 through which ground was formerly supplied to the green lamp and to the electro pneumatic valve EPV is broken and consequently, the electro pneumatic valve EPV drops its stem, thereby permitting air to exhaust from the chamber 72 through the port 49 and the whistle 5, which audibly warns the engineman to be on the alert for a possible change of signal indication at armature 57 and its associated contact member 57 f and contact 75, a third point in the traced circuit for the green lamp 62 is interrupted, and at the associated contact 76 a point in a circuit for the red lam 64 is prepared.

Since the associate electromagnet trackway element of block A has its windings 98 and 99 energized the polarity of this electro: magnet is opposite to that of the permanent magnet 95 and consequently, as the receiver passes over this electromagnet trackway element the armatures 55, 56, and 57 are rotated back into the position in which they are shown in Figs. 1 and 3. The formerly traced circuits for lighting the green lamp 62 and for energizing the electro pneumatic valve EPV are therefore immediately reestab-i lished and the actuation of the whistle '5 ceases. These signal changes serve to indicate to the engineman that they have entered a block under favorable traflic conditions, and therefore no action on the part of the engineman is required. When the vehicle 101 reaches the exit portion of block B, the receiver R passes over the permanent magnet trackway element 95', which causes the armaturesof the relay R to be operated to bring about the same circuit changes as when the receiver passed over the trackway magnet 95. Since, however, the block D is occupied the trackway circuits at the entrance to block C are such that the caution windings 96 and 97 of the electromagnet trackway element, positioned a short distance in advance of the permanent magnet trackway element 95, are energized. Consequently, the magnetic field set up by this trackway electromagnet is at right angles to that set up by the permanent magnet trackway element 95. When the receiver R passes over this trackway electromagnet only the armature 57 is restored, as illustrated in Fig. 4. Since the circuit for the green lamp 62 remains interrupted at contact 7 3 and contact member 55',and also atcontact member 56 and contact 74, the green lamp remains extinguished. Also, since the circuit for the electro pneumatic valve EPV must also pass through contact member 56 and contact 74, the electro pneumatic valve remains deenergized and the whistle 5 continues to sound and serves to audibly warn the engineman of adverse trafiic conditions ahead. Ordinarily, the engineman will heed the warning given by the whistle 5 and will proceed to forestall an automatic brake application by operating the acknowledging key 61 momentarily. WVhen this key is operated, a circuit is completed for the armature restoring winding 60, via conductors and 71, and the armature 56 is thereby restored to its initial position in which it is shown in Fig. 1. The formerly traced circuit for the electro pneumatic valve EPV is therefore reestablished through contact 74 and contact member 56 as soon as the acknowledging key 61 is returned to its normal position. This results in the port 49 being again closed and in the whistle ceasing operation. The armature 57 in operating, at its contact member 57 and contact 7 5 closed a point in the circuit of the yellow lamp 63 which is completed following the acknowledging action from the negative terminal of the battery 84, through conductor 71, armature 57 and its contact member 57, the contact 75, conductor 88, armature 55, its contact member 55, contact 7 2, conductor 66, the yellow lamp 63, conductor 69, conductor 67, contact 74, contact member 56, conductor 86 and through the normal contacts of the acknowledging key 61 to the positive terminal of the battery 84. The yellow lamp 623 is therefore lighted as the vehicle 101 progresses through block C and until the next signal change occurs as the Vehicle passes over the permanent trackway magnet \Vhen the receiver R passes over the trackway magnet 95 the armatures 56 and 57 are again rotated into the position in which they are shown in Fig. 2 and consequently, the effect of having passed over the electromagnet trackway element at the exit of block C is entirely wiped out. Since the block D is occupied by a vehicle 181, causing the armatures 126 and 127 of the polarized relay 104 to assume their neutral or mid position, the circuits through all windings of the electroma 'net trackway element immediately in advance of the permanent magnet trackway element 95 are open. The circuit conditions which are se up by the receiver R in passing ov'r the tree-away m H1611 95 therefore remains and since the whistle 5 continues to sound, the enginemen are audibly informed that acknowledgment is again necessary.

Responsive to the acknowledging action, as in the case when acknowledgment was made at exit of block (I, armature 56 is rotated in a counter-clockwise direction, while the armatures and 57' remain into attracted relations with respect to the pole pieces 78 and 82, respectively. The formerly traced circuit for the electro pneumatic valve EPV is therefore again established and the whistle 5 silenced. A circuit is also completed for the red lamp 64. This circuit extends from the negative pole of the battery 84, through conductor 71, the contact member 57 contact 7 6, conductor 68, red lamp 64, the conductor 67, contact 74, contact member 56, and over the conductor 86 and the acknowledging key 61 to the positive terminal of the battery 84. The lighting of the red lamp serves to warn the enginemen that they are entering a block which is already occupied and that they must proceed with extreme caution.

it will now be assumed that the enginemen fail to acknowledge within the six seconds of time interval allowed after passing the trackway magnet 95 Under these circumstances, at the end of the six-second interval, sufficient air has been exhausted from the chamber 72 out through the whistle 5 to permit the air pressure on the right side of the piston 19 to become effective to move it and the valve member 20 to the left. The movement of the valve member closes the normally open passage extending between openings 7 and 8 via part 7, port 10, and the double heading cock, thereby preventing the brake pipe from being recharged while the slide valve member 20 is in its operated position. The movement of the slide valve member 20 also connects the port 10 to the service exhaust port 11 via by-pass 90, thereby causing a brake pipe pressure reduction suilicient to cause a service brake application.

To release the brakes, after an automatic application, the engineman must first operate the acknowledging key 61 which, in a man ner already described, is effective to energize tne electro pneumatic valve EPV and to complete the circuit for the yellow or red lamp, depending on the condition of the receiver R. The energization of the electro pneumatic valve EPV, as previously explained, stops the actuation of the whistle 5 and the exhaust of air from chamber 72. The air pressure in chambers 71 and 72 therefore again rises at a rate determined by the port 22 and the ca- 1 pacity of'the reservoir 50. As soon as the pressure rises to a point where it approximates that on the right side of the piston 19 the spring 21 will return the piston 19 and the valve member 20 to their normal positions, in which they are shown, thus closing the passage 14 and again opening the reservoir 50 to atmosphere through the by-pass in valve member 20 and the exhaust port 12. The slide valve member 20 in returnin to its normal position also again blankets e exhaust port 11 and again connects the opening 7 of the valve member with the brake pipe opening 8. This (permits the brake pipe to be again recharge in the usual manner from the usually provided main reservoir through the brake applicator valve (not shown) and the automatic brake valve structure.

If, after receiving an automatic brake a plication, the enginemen desires to amplii y the application he can do so by moving the handle of the brake applicator valve to the emergency position. This causes an instantaneous exhaust of air to occur through the emergency port of the brake a plicator valve and results in a very uick re notion in pressure being made in t e air pressure on the left side of the emergency application piston 32. This permits the air on the ri ht side of the piston 32 to rapidly expand an move the emergency application piston 32 to the left. As soon as this piston has moved a slight distance, its continued movement is'assisted by air sup lied to the right of the piston from the bralie pipe via the port 10' and the port 91. The movement of the piston 32 to the extreme left connects the port 10', via by-pass 73 to the lar e emergency exhaust port 37. This quick r notion in the brake line results in an emergency application of the brakes.

It has been proposed that installations of cab signalling be made without the provision 0 any train stop equipment. The resent system is ideal for an installation 0 this kind. In an installation of this kind, the electro pneumatic valve EPV and whistle 5 or their equivalent will be connected directly with the main reservoir; the visual and audible signal control equipment will function in the same manner as when used in conjunction with the brake applicator valve; and the enginemen will be required to acknowledge as in the train stop system.

From the foregoing it will be a preciated that applicant has succeeded in eveloping train control and the cab signalling equipment which is very simple and will operate in an absolutely reliable manner.

What is claimed is:

1. In a cab si alling system, lamps for indicating clear caution, and danger, conditions, respectively, a trackway element at the exit of each block of a trackway for inductively transmitting an impulse to cause any lighted signal to be extinguished and a circuit for the danger indicating lam to be repared when a vehicle carryizn signa s (passes a definite point in a bloc and a secon trackway element subsequently encountered at the exit of each block effective to cause the clear indicating lamp to lighted in certain instances.

2. In a cab signalling system, lamps for indicating clear caution, and danger conditions, respectively, a trackwa element at the exit of each block of a trac way for inductively transmitting an impulse to cause any lightedsignal to be extinguished and a circuit for the danger indicating lamp to be prepared when a vehicle carryin signals passes a definite point in a bfo second trackwa countered effective to prepare a circuit for said caution lamp incertain instances, and manually operable means for completing the circuit prepared.

3. In a cab si alling system, lamps for indicating clear caution, and danger conditions, respectively, a trackwa element at the exit of each block of a trac way for causing any lighted signal to be extinguished and a circuit for the danger indicating lamp to be prepared when a vehicle carrying such signals passes a definite point in a block, an audible signal also set into operation by said trackway element, and a second trackway element subsequently encountered effective if traflic conditions ahead are favorable to light the clear lamp and to stop the operation of said audible si al and efl'ective at times if the traffic conditions are unfavorable for preparing a circuit for said can tion lamp only.

4. In a cab s' ailing system, lamps for indicating clear caution, and danger conditions, respectively, trackway elements at the exit of each block of a trackwa for causing any lighted signal to be extinguished and a circuit for the danger indicating lamp to be prepared when a vehicle car g such signals passes a definite point in a bid 2k, an audible signal also set into operation by said trackway element, a second trackway element subsequently encountered effective to light the clear lamp and to cause the operation of said audible signal to cease, under certain traflic conditions; efiective under certain other trafiic conditions to merely prepare a circuit for said caution lamp; and inert under still another traflic condition; and acknowledging means efi'ective when operated to complete a circuit for the caution or danger lamp depending on the consuch ck, s. element subsequently em its dition of the second trackway element passed.

5. In a train stop system, a receiver relay having three armatures and associated contacts, trackway elements effective when encountered by said relay to move all of said armatures from one position to another, an-

other trackway element efi'ective when cm countered to restore certain of or all said armatures depending on traflic conditions in advance, and cab signals and train stop apparatus under control of said relay.

6. In a device for inductively transmitting magnetic impulses to a relay, a set of four electromagnets connected to form a rectangle, two of said electromagnet windings when energized causing a magnetic field to be set up in one direction and the other two of said magnet windings when energized setting up a magnetic field at right angles to the field set up by the first energized electromagnet windings.

7 In a device for inductively transmitting impulses, tour pole pieces, four electromagnet windings connecting said pole pieces and electromagnets in a loop, each of said pole pieces being between two different electromagnet windings so that either of two of said windings may produce a magnetic field in the same pole piece.

8. In a device for inductively transmitting impulses, four pole pieces, electromagnet windings connecting said pole pieces into a rectangle, two of said windings when energized being efiective to oppositely polarize the pole pieces nearest each other, the other two windings being effective when energized to oppositely polarize. the pole pieces farthest from each other.

9. In a cab signalling system, lamps for indicating clear, caution, and danger conditions, respectively, a trackway magnet midway adjacent the rails at the exit of each block of a trackway for inductively transmitting an impulse to cause any lighted signal to be extinguished and a circuit for the danger indicating lamp to be prepared it not already prepared, when a vehicle carrying such signals passes a definite point in a block, and a second trackway magnet, located adjacent the rails in the same relation thereto as is the first mentioned magnet, encountered at the exit of each block and effective: to cause the clear indicating lamp to be lighted in certain instances and the caution lamp circuit to be prepared in other instances.

10. In a device for transmitting magnetic impulses, a pair of magnet cores placed parallel to each other with a third core having a winding thereon and being placed at rightangles to the parallel cores, and windings for said parallel cores energizable to set up a magnetic field about said cross at rightangles to the magnetic field of the third core.

11. In a cab signalling system, lamps for indicating clear, caution, and danger conditions, respectively, a trackway element at the exit of each block of a trackway for inductively transmitting an impulse to cause any lighted signal to be extinguished when a vehicle carrying such signals passes a definite point in a block, and a second trackway element subsequently encountered at the 

